Impact of feeding organic selenium supplement on growth performance, nutrients digestibility and some blood metabolites of fattening lambs

Trace minerals, as metabolic modifier agents, increase nutrients utilization efficiency in domestic animals. Selenium has important metabolic and antioxidant functions in animal cells. However, there is not enough information regarding selenium requirements of Iranian local sheep. Therefore, the aims of this study were to investigate the effects of feeding selenium-methionine (Se-Met) supplement on growth performance, nutrients digestibility, ruminal fermentation status and some blood metabolites of fattening male lambs.

Fifteen Kermani male lambs with average body weight of 32.2 ± 1.09 kg were assigned to 3 treatments with 5 replicates each, as a completely randomized design for 10 weeks including 2 weeks of adaptation and 8 weeks of data collection. The experimental treatments were (1) basal diet without supplemental Se, (2) basal diet plus 0.5 mg/kg diet of Se-Met, and (3) basal diet supplemented with 1 mg/kg of Se-Met. Daily feed intake and body weight were measured. The nutrients digestibility was determined via total feces collection method at the end of study. Sampling from the rumen fluid was done on the last day of the final week of the experiment just two hours after morning feeding using the esophagus-tube connected to vacuum pump for pH and ammonia nitrogen determination. Blood samples were also drawn from jugular vein at the end of experiment and serum was used for metabolite analysis. The statistical analysis of data was done by using SAS software.

Based on the results, average daily feed intake and gain were not affected by the experimental treatments (P>0.05). However, lambs fed 0.5 mg Se-Met tended to have improved feed conversion efficiency compared with those on the control diet (P=0.07). Feeding male lambs with 1 mg/kg of Se-Met supplement increased dry matter and organic matter digestibility compared to the control lambs (P<0.05). Despite the higher values for fat as well as neutral and acid detergent insoluble fiber digestibility, their difference with that of the control was not statistically significant. Moreover, NH3-N concentration and pH of ruminal fluid were not affected by the experimental treatments (P>0.05). Feeding 1 mg/kg of Se-Met increased serum glucose concentration (P=0.03), however, serum total protein, triglyceride and urea concentrations were not different among experimental groups (P>0.05).

It can be concluded that dietary supplementation of 0.5 mg Se-Met/kg of diet improves feed conversion efficiency and 1 mg Se-Met increases dry matter and organic matter digestibility as well as blood glucose of fattening lambs without any adverse effects on ruminal pH and ammonia nitrogen concentration